The first traversable wormhole is the Ellis wormhole constructed in 1973, as an exact solution of Einstein gravity coupled to a free phantom scalar field [1]}. The Ellis wormhole is spherically-symmetric and static and it is a massless wormhole, symmetrically connecting two flat spacetimes. Later in same year, Bronnikov found that there was a more general wormhole solution in the theory [2]}, [3]}. Bronnikov wormhole is massive and asymmetric. In the massless limit, the Bronnikov solution reduces to the Ellis solution. Since then, many new wormhole solutions have been constructed in Einstein gravity or modified gravity theories [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}.
